Differences in ecological and geographical circumstances can result in the evolution of important intraspecific changes in various life history and reproductive biology traits. Clutch size can be shaped by the risk and pressure of predation (on individuals and/or nests) and the intensity of intraspecific competition. The island syndrome hypothesis (ISH) proposes that clutch sizes on islands are smaller than those of their mainland counterparts. I studied three populations of an oviparous lizard (Japalura swinhonis) on Kenting, Green Island and Orchid Island in Taiwan. The lizard lives under similar climatic conditions but differ in risk of predation and competition. I predicted that island populations would form larger, but fewer offspring because mesopredator release amplifies lizard population density, which leads to high intra-specific competition that selects for small clutches of relatively large offspring that hatch quickly. These predicted responses could differ, however, if selection is further imposed by high depredation rates on eggs. Here, I compare lizard clutch sizes (Japalura swinhonis) among three localities (Kenting, Orchid Island, and Green Island) to test whether risk of predation from egg-eating snakes (Oligodon fomasanus) influences reproductive tradeoffs. On Green Island, where egg-eating and lizard-eating snakes are uncommon, lizard population density was highest, clutch size was smallest, incubation took the longest, and hatchling lizards were no difference in body mass and SVL with Orchid Island. On an island where egg-eating snakes are extremely abundant (Orchid Island; Lanyu), lizard population density was the same as that at Kenting, clutch sizes were moderate, incubation time was as long as that on Green Island. At Kenting, where egg-eating snakes are rare, but lizard-eating snakes are plentiful, lizard population density was low, clutch sizes were large, total weight of egg mass was heaviest and incubation was shortest, but hatchlings were extremely large. The snout-vent length of females was smallest at Kenting. I assume that females altered their life histories to lay more clutches by means of reaching sexual maturity earlier, which is beneficial when adult survival is low due to depredation by multiple predators. Our field and lab experiments demonstrate that predation can directly influence island lizard reproductive traits by exerting strong selective forces favoring mechanisms to reduce exposure to predators.島嶼效應是指生物從大陸遷徙到島嶼之後，因為環境資源的變化，生物從外在形態、行為甚至生活史產生改變以適應環境。本研究以斯文豪氏攀木蜥蜴 (Japalura swinhonis) 從台灣遷徙到綠島和蘭嶼三地的分布做為研究材料。我進行野外族群密度、掠食者密度與種類調查等；並佐以實驗室養殖母蜥進行生殖實驗，項目包含比較三地公母蜥吻肛長、蜥蜴窩卵數、蛋總重 (clutch mass)、孵化期、窩間距、幼蜥吻肛長、幼蜥重量和母蜥吻肛長與窩卵數相關性等。結果顯示，墾丁和綠島符合島嶼效應的假說，但蘭嶼因為吃蛋的掠食者 (赤背松柏根) 族群太大，而改變了蘭嶼斯文豪氏攀木蜥蜴的生蛋策略。島嶼蜥蜴的生殖策略也許非單一力量所影響造成的，可能是多重演化力量同時作用而有權衡(tradeoffs)現象發生而造就斯文豪氏攀木蜥蜴今日的生蛋模式。